Stcr. XVII. i. CATENATION OF MOTIONS. 225 



tenations. So vertigo produces vomiting, and a 

 great fecretion of bile, as in fea-ficknefs, all thefe 

 being parts of the tribe of irritative catenations. 



8. Weaker catenated trains may be diffevered 

 by the fudden exertion of the (Ironger. When a 

 child firft attempts to walk acrofs a room, call to 

 him, and he inftantly falls upon the ground. So 

 \vhile I am thinking over the virtues of my friends, 

 if the tea-kettle fpurt out fome hot water on my 

 flocking ; the fudden pain breaks the weaker chain 

 of ideas,, and introduces a new group of figures of 

 its own. This circumflance is extended to fome 

 unnatural trains of action, which have not been 

 confirmed by long habit ; as the hiccough, or an 

 ague-fit, which are frequently curable by iurprife. 

 A young lady about eleven years old had for five 

 days had a contraction of one mufcie in her fore 

 arm, and another in her arm, which occurred four 

 or five times every minute ; the mufcies were feen 

 to leap, but without bending the arm. To coun- 

 teract this new morbid habit, an iflue was placed 

 over the convulfed mufcie of her arm, and an 

 adhefive plafter wrapped tight like a bandage over 

 the whole fore arm, by which the new motion* 

 were immediately deflroyed, but the means were 

 continued fome weeks to prevent a return. 



9. If any circle of actions is difTevered, either 

 by omiflion of fome of the links, as in fleep, or 

 by infertion of other links, as in furprife, new ca- 

 tenations take place in a greater or lefs degree. 

 The lad link of the broken chain of actions be- 

 comes connected with the new motion which has 

 broken it, or with that which was neareit the link 

 omitted ; and thefe new catenations proceed inftead 

 of the old ones. Hence the periodic returns of 

 ague-fits, and the chimeras of our dreams. 



10. If a train of actions is diflevered, much ef- 

 fort of volition or fenfation will preveju its being 



reftored. 



